Problem: Ishaan is $3$ times as old as Christopher and is also $14$ years older than Christopher. How old is Christopher?
Answer: We can use the given information to write down two equations that describe the ages of Ishaan and Christopher. Let Ishaan's current age be $i$ and Christopher's current age be $c$. Let Ishaan's current age be $i$ and Christopher's current age be $c$. ${i = 3c}$ ${i = c + 14}$ Now we have two independent equations, and we can solve for our two unknowns. Since we are looking for $c$, and both of our equations have $i$ alone on one side, this is a convenient time to use elimination. Subtracting the second equation from the first equation, we get: $0 = {3c} -{(c + 14)}$ which combines the information about $c$ from both of our original equations. Solving for $c$, we get: $2 c = 14$. $c = 7$.